The invention generally relates to semiconductor manufacturing and, more particularly, to device structures, fabrication methods, and design structures for a biological or chemical sensor.
Biological and chemical sensors based on ion-sensitive field effect transistors (ISFET) can be integrated with modern microelectronic devices and used to detect and measure various aspects of chemical reactions and substance properties. For example, an ion-sensitive field effect transistor (ISFET) may be used to measure ion concentrations, such as hydrogen ion concentration, in a sample of an analyte. An ISFET is similar to a metal oxide semiconductor field effect transistor (MOSFET), but lacks a gate electrode. Instead, an ion-sensitive membrane is placed over the channel region of the ISFET and is exposed to the analyte sample. A reference electrode of the ISFET is separated from the ion-sensitive membrane by the solution. The potential difference between the channel and the reference electrode is a function of the ion concentration in the analyte sample. An operating characteristic of the ISFET may be measured and used to calculate ion concentration.
Improved device structures, fabrication methods, and design structures for a biological and chemical sensor are needed.